Application: gvSIG desktop » gvSIG scripting

"""JSON token scanner

"""

import re

def _import_c_make_scanner():

    try:

        from simplejson._speedups import make_scanner

        return make_scanner

    except ImportError:

        return None

c_make_scanner = _import_c_make_scanner()

__all__ = ['make_scanner', 'JSONDecodeError']

NUMBER_RE = re.compile(

    r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',

    (re.VERBOSE | re.MULTILINE | re.DOTALL))

class JSONDecodeError(ValueError):

    """Subclass of ValueError with the following additional properties:

    msg: The unformatted error message

    doc: The JSON document being parsed

    pos: The start index of doc where parsing failed

    end: The end index of doc where parsing failed (may be None)

    lineno: The line corresponding to pos

    colno: The column corresponding to pos

    endlineno: The line corresponding to end (may be None)

    endcolno: The column corresponding to end (may be None)

    """

    # Note that this exception is used from _speedups

    def __init__(self, msg, doc, pos, end=None):

        ValueError.__init__(self, errmsg(msg, doc, pos, end=end))

        self.msg = msg

        self.doc = doc

        self.pos = pos

        self.end = end

        self.lineno, self.colno = linecol(doc, pos)

        if end is not None:

            self.endlineno, self.endcolno = linecol(doc, end)

        else:

            self.endlineno, self.endcolno = None, None

    def __reduce__(self):

        return self.__class__, (self.msg, self.doc, self.pos, self.end)

def linecol(doc, pos):

    lineno = doc.count('\n', 0, pos) + 1

    if lineno == 1:

        colno = pos + 1

    else:

        colno = pos - doc.rindex('\n', 0, pos)

    return lineno, colno

def errmsg(msg, doc, pos, end=None):

    lineno, colno = linecol(doc, pos)

    msg = msg.replace('%r', repr(doc[pos:pos + 1]))

    if end is None:

        fmt = '%s: line %d column %d (char %d)'

        return fmt % (msg, lineno, colno, pos)

    endlineno, endcolno = linecol(doc, end)

    fmt = '%s: line %d column %d - line %d column %d (char %d - %d)'

    return fmt % (msg, lineno, colno, endlineno, endcolno, pos, end)

def py_make_scanner(context):

    parse_object = context.parse_object

    parse_array = context.parse_array

    parse_string = context.parse_string

    match_number = NUMBER_RE.match

    encoding = context.encoding

    strict = context.strict

    parse_float = context.parse_float

    parse_int = context.parse_int

    parse_constant = context.parse_constant

    object_hook = context.object_hook

    object_pairs_hook = context.object_pairs_hook

    memo = context.memo

    def _scan_once(string, idx):

        errmsg = 'Expecting value'

        try:

            nextchar = string[idx]

        except IndexError:

            raise JSONDecodeError(errmsg, string, idx)

        if nextchar == '"':

            return parse_string(string, idx + 1, encoding, strict)

        elif nextchar == '{':

            return parse_object((string, idx + 1), encoding, strict,

                _scan_once, object_hook, object_pairs_hook, memo)

        elif nextchar == '[':

            return parse_array((string, idx + 1), _scan_once)

        elif nextchar == 'n' and string[idx:idx + 4] == 'null':

            return None, idx + 4

        elif nextchar == 't' and string[idx:idx + 4] == 'true':

            return True, idx + 4

        elif nextchar == 'f' and string[idx:idx + 5] == 'false':

            return False, idx + 5

        m = match_number(string, idx)

        if m is not None:

            integer, frac, exp = m.groups()

            if frac or exp:

                res = parse_float(integer + (frac or '') + (exp or ''))

            else:

                res = parse_int(integer)

            return res, m.end()

        elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':

            return parse_constant('NaN'), idx + 3

        elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':

            return parse_constant('Infinity'), idx + 8

        elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':

            return parse_constant('-Infinity'), idx + 9

        else:

            raise JSONDecodeError(errmsg, string, idx)

    def scan_once(string, idx):

        if idx < 0:

            # Ensure the same behavior as the C speedup, otherwise

            # this would work for *some* negative string indices due

            # to the behavior of __getitem__ for strings. #98

            raise JSONDecodeError('Expecting value', string, idx)

        try:

            return _scan_once(string, idx)

        finally:

            memo.clear()

    return scan_once

make_scanner = c_make_scanner or py_make_scanner